Treatment of petroleum distillates



Patented Nov. 20, 1951 TREATMENT OF PETROLEUM DISTILLATES ErvingArundale, Westfield, and John P. Thorn,

Cranford, N. J assignors to Standard Oil Development Company, acorporation of Delaware Application September 3, 1949, Serial No.113,942

12 Claims. 1

The present invention is concerned with an improved process for theproduction of high quality petroleum products. The invention is moreparticularly concerned with the production of high quality petroleumproducts boiling below about 700 F. especially those products which boilin the motorfuel boiling range. In accordance with the present processobjectionable sulfur compounds, as for example mercaptans, are removed.from petroleum distillates containing the same or are converted torelatively innocuous compounds by treating the distillates with analkylene oxide in the presence of an alkaline catalyst.

In the production of high quality petroleum products, as for example inthe production of petroleum products boiling in the motor fuel boilingrange, it is known to use various procedures either to remove mercaptansfrom the oil or to convert these mercaptans to less objectionable sulfurcompounds. A few of the conversion processes comprise copper sweetening,Doctor treatment, hypochlorite sweetening, air sweetening and the like.Processes which remove mercaptans or reduce thesulfur content of the oilcomprise caustic treatment and treatment with sulfuric acid. While theseprocesses are in general satisfactory, they all have certain limitationswhich to some extent control their utilization. For example in thecopper and Doctor sweetening processes the treating agent must beregenerated for economical operation and, in certain instances,objectionable emulsions are formed. The hypochlorite and air sweeteningprocesses can be applied to cracked distillates but the products usuallycontain high gum contents. Acid treating is an efiective means forreducing the sulfur content of petroleum fractions but, in the case ofcracked gasolines, high polymer losses and a reduction in octane numberare experienced. Finally treatment with aqueous caustic solutions alonei not entirely satisfactory since the higher mercaptans are not removedin such a process. To present process employing an alkylene oxide in thepresence of an alkaline catalyst produces a satisfactory sweetenedproduct in an efficient and economical operation.

The present invention may be understood by reference to the drawingillustrating one embodiment of the same. An oil feed stream, which forthe purpose of illustration is assumed to comprise a naphtha boiling inthe range from about 80 F. to 450 F. and containing mercaptans,

is introduced into the system by means of feed line I. A causticsolution, which for the purpose of illustration is assumed to be anaqueous solutioncontaining 15% sodium hydroxide by weight, is added tothe oil in line I by means of line 2. The respective streams are mixedin orifice mixer or equivalent means 3. The stream is then in troducedinto settling zone 4 wherein a caustic phase and an oil phase form. Thelower caustic phase can be removed by means of line 5 and regenerated orrecycled to line 2 via line l3. The treated oil phase isremoved by meansof line 6 and mixed with additional sodium hydroxide solution which isintroduced by means of line 1.

Although the concentration of the caustic solution may vary appreciablyit is assumed that a 15% by weight caustic soda solution is employed.

In accordance with the present invention an alkylene oxide, as forexample ethylene oxide, is then introduced by means of line 8 and therespective streams are thoroughly mixed by passing through an orificemixer or equivalent mixing device 9. The stream is introduced intosettling Zone l0 wherein an oil phase and a spent caustic phaseseparate. The upper oil phase free of mercaptans is removed from settlerID by means of line H and further refined as desired. This stream ispreferably water washed and may in some instances be rerun, althoughthis latter operation is only necessary if maximum sulfur reduction isdesired. The caustic phase is withdrawn from the bottom of zone H) bymeans of line l2 and may be Withdrawn from the system. However, ingeneral, it is preferred to recycle this stream and introduce it intothe oil feed stream by means of line l3 or line 1.

Sour virgin or cracked hydrocarbon distillates can be treated in thismanner and the process of the present invention secures advantage overacid treating in that; (a) the products do not require rerunning; (b)there is no poly mer loss in the case of cracked distillates and; (c)the octane number is not degraded.

The treating agent of the present invention comprises the use of analkylene oxide in the presence of an alkaline catalyst. In general thealkylene oxide has the formula wherein R1, R2, R3, and R4 representhydrogen atoms or alkyl groups containing from 1 to 2 carbon atoms.Satisfactory oxides are for example, ethylene oxide, propylene oxide,butylene oxide, isobutylene oxide, trimethylethylene oxide, and thelike. The preferred treating agent comprises ethylene oxide (CH2OCH2).

The alkaline catalyst preferably comprises an alkali metal hydroxidesolution, as for example,

a sodium hydroxide solution. Other alkaline catalysts which may be used,are potassium hydroxide, ammonium hydroxide, sodium carbonate or sodiumbicarbonate.

The concentration of the respective treating" agents employed will varyappreciably depending upon the character of the oilbeing treated, as

well as, upon the character and concentration of the mercaptanconstituents present. In general, it is preferred to employ from 0.05 to5% by weight of the alkylene oxide based upon the weight of the oilbeing treated. The concentration will vary with the copper number andboiling range of the feed stock and the treating temperature, but willpreferably be in the range from about 0.2 to. 0.8 weight percent. Theamount of aqueous alkaline catalyst employed is preferably in the rangefrom 5 to by volume based upon the volume of the oil being contacted butmay vary from 1 to by volume. The concentration of the aqueous alkalisolution is preferably in the range from 5% to 20% by Weight of alkalihydroxide based upon the total weight of the aqueous alkali solutionalthough concentrations as high as 50% or as low as 1% can be employed.

The temperatures employed, as well as the pressure, may be variedappreciably. However, in general it is preferred that the temperature bebelow about 212 F. preferably in the range from 70 to 140 F. The timeo'ftreatment may vary considerably depending on other operat-"- ingconditions. In general the time of contact varies from about 2 to 15minutes. The process of the present invention may be more fullyunderstood by the following examples illustrating embodiments of thesame:

EXAMPLE 1 346 grams (500 cc.) of virgin naphtha of copper number 1 wereplaced in a one-quart pressure bottle. 50 cc. of a 5% sodium hydroxidesolution and 3.4 grams of ethylene oxide were added and the batch shakenat room temperature for hour. The caustic layer was separated and thenaphtha layer water washed twice with .50 cecrwater. The water wasremoved and the product filtered. This treated product had a coppernumber 01? one.

1 Milligrams of mercaptan sulfur per cc.

EXAMPLE 2 Additional operations were conducted in which the causticsolution concentration, quantity of. causticsolution, and amount andtype of alkylene oxide were varied. The feed stocks comprised a sourvirgin naphtha and a sour thermally cracked gasoline. Prior tocontacting these 'n'ap'hthas with the a'lkylene oxide-caustic solution,theywere washed in an initial stage with 10 volume percent of 5% sodiumhydroxide solution and then withlO vo1ume percent of waterin order toremove'h'ydrogen sulfide and caustic soluble mer'-' captans and therebydecrease the amount of alkylene oxide required. 500 cc. of the causticwashed hydrocarbon distillate were shakenat room temperature (unlessotherwise specified) for 15 minutes with a'caustic soda solution both inthe presenceand absence of small amounts ofethylene, propylene andisobutylene oxides. The batch was then allowed to settle, thecausticlayer was removed, and the hydrocarbon layer washed with '20'voluine'percent' of waterbefore the copper number was determinedthereon; The results of "these operations are. as "follows:

Allc'ylene oacz'd-e swecteninooj petroleum distillates SO-UR VIRGINNAPHDHA 1 per cent 40 wt. per cent 15 wt. per cent 15 wt. per cent 15Wt. percent 15 wt. per "cent 15 wt.

. per cent 15 wt. per cent 15 wt. per-cent 15 wt.

' per cent '5 wt; per cent caustic 2 alone per cent 10 wt. percentcaustic 9 alone percent 15 wt. percent caustic 1 alone. per cent-25 wt.per cent'caustic 1 alone. per cent 40 wt. per cent caustic al0ne W .percent 5 wt. per-cent caustic+0.8 wt. per cent ethylene oxide per cent 10wt. per cent caustic+0.8 wtxperccnt ethy lenc oxide per cent 15 wt. percent caustic-{-03 wt. per cent zawt. per cent cl'ai1stic+0.8 wt...

percentcaustic {-0.8 wt.

per cent 'ciustidi-OJ wt; V 'p'ercentcaustic+0.4 wt. per cent ethyleneoxide per cent caustic+06 wt. per cent-ethylene'oxide per centcaustie+02wt per cent propyiene oxide. per cent'caustic +0.4 wt. percentpropylene oxide. per cent caustic+0.6 wtj'per cent propylene oxide.per cent caustic l0.2 wt. per'cent isobutylene oxid per cehtcaustic-l-OAwt. per cent isobutylene oxid percent 15 wt. per cent caustic+0.6 wt.per cent iscbutylei'ie-oxide 5 Vol. per cent mm. per cent caustic+0.2wt. per cent ethylene oxide. 5 Vol. percent l5 w't. percentca'usticfi-OA wtper cent ethylene oxide- 5 Vol. per cent 15 wt. percent caustic+0.6 wt. per cent ethylene oxida 20 Vol. percent 15 wt. per'cent caustic+0.2 wt. per cent ethylen'eoxide 20 Vol. percent 15 wt. percent caustic-H14 Wt. per cent ethylene oxide 20 Vol. per cent 15 wt. percent caustic-F06 Wt.-p'cr centethylene oxide... 10 V01. per cent-l5 wt.per cent caustic+0.2 wt per cent ethylene oxide-(1'31 10 Vol. per cent15 wt. per cent caustic-+0.4 wt. percent ethylene oxide (131; 7

10 V01. per cent 15 wt. per cent caustic+0.6 Wt. percent ethyleneo'xiie*(l31 -F. e r

1 Coppcr number of untreated stock=50, after initialpaustic washing iii.Brominenumher 1.7, cgJg-risp: gray. 0.675; 1 Caustic means aqueoussodium hydroxide solution. J

Alkylene oxide sweetening of petroleum distillates Continued soonTHERMALLY oaxoxnn NAPHTHAI Treatment Copper No. of Product per cent wt.per cent caustic alone. per cent wt. per cent caustic a1one per cent 10wt.

. per cent wt. per cent wt. per cent 15 wt. per cent 15 Wt. per cent 15Wt. per cent 15 wt. per cent 15 wt. per cent 15 wt. per cent 15 wt. percent 15 wt. per cent 15 wt.

10 V01. per cent 15 wt.

. per cent 5 wt. per cent caustic alone .per cent 25 Wt. per centcaustic a10ne. :T TII: n per cent 40 wt. per cent caustic alone per cent5 wt. per cent caustic+0.8 per cent ethylene oxide per cent 15 wt. percent caustic+0.8 per cent ethylene oxide percent caustic+0.6 wt. percent ethylene oxide per cent eaustic+0.2 wt. per cent propylene oxide.per cent caustic+0.4 wt. per cent propylene oxide. per cent caustic+0.6wt. per cent propylene oxide. per cent caustic+0.2 wt. per centisobutylene oxide per cent caustic-+0.4 wt. per cent isobutyleneoxideper cent caustic+0.6 Wt. per cent isobutylene oxide... 5 Vol. percent 15 wt. per cent caustic+0.2 wt. per cent ethylene oxide 5 Vol. percent 15 wt. per cent caustic+0A wt. per cent ethylene oxide.

20 Vol. per cent 15 wt. per cent caustic+0.4 wt. per cent ethyleneoxide- 20 Vol. per cent 15 wt. per cent caustic+0.4 wt. per centethylene oxide 20 Vol. per cent 15 wt. per cent caustic+0.6 wt. per centethylene oxide. 10 Vol. per cent 15 wt. per cent caustic-{-02 wt. percent ethylene oxide (131 F.) 10 Vol. per cent 15 wt. per centcaustic+0.4 wt. per cent ethylene oxide (131 F.)... per cent caustic+0.6wt. per cent ethylene oxide (131 F.)

3 Copper number of untreated stock==20, after initial caustic washing16. Bromine number 65.5, sp. gray. 0.755.

It will be noted that in the presence of the alkylene oxide, a definitereduction in copper number was obtained which could not be realized whentreating with the caustic solution alone.

The invention is broadly concerned with the use of alkylene oxides forthe removal or conversion of mercaptan compounds from petroleum oilsboiling below about 700 F. The invention is particularly concerned withthe use of ethylene oxide in conjunction with an alkali hydroxidesolution for the removal or conversion of mercaptan compounds frompetroleum oils boiling in the motor fuel boiling range (80 F. to 430F.).

Having described the invention it is claimed:

1. Process for the conversion of mercaptan compounds in a petroleum oilcontaining the same into relatively innocuous compounds which comprisescontacting said petroleum oil with an alkylene oxide in the presence ofan alkaline catalyst, said alkylene oxide being selected from the classof compounds represented by the structural formula Ra R:

wherein R, is selected from the class consisting of hydrogen and alkylgroups containing from 1 to 2 carbon atoms.

2. Process as defined by claim 1 wherein said petroleum oil boils in therange below about 700 F.

3. Process as defined by claim 1 wherein said petroleum oil comprises amotor fuel boiling in the range from about 80 F. to 450 F.

4. Process as defined by claim 1 wherein said alkylene oxide comprisesethylene oxide.

5. Process as defined by claim 1 wherein said alkylene oxide comprisespropylene oxide.

6. Process as defined by claim 1 wherein said alkylene oxide comprisesisobutylene oxide.

7. Process as defined by claim 1 wherein said alkaline catalystcomprises an alkali metal hydroxide solution containing from about 5 to50% by weight of said alkali metal hydroxide.

8. Process as defined by claim 1 wherein the temperature used is belowabout 212 F.

.9. Process as defined by claim 1 wherein the concentration of thealkylene oxide used is in the range from about .05 to 5% by weight basedupon the feed oil.

10. Process as defined by claim 1 wherein the concentration of thealkylene oxide used is in the range from about 0.2 to 0.8% by weightbased upon the feed.

11. Process as defined by claim 1 wherein said alkaline catalystcomprises an alkali metal hydroxide solution containing from about 5 to50 by weight of said alkali metal hydroxide and wherein the amount ofsaid alkaline catalyst utilized is from about 1 to 20% by volume basedupon the volume of petroleum oil being contacted.

12. Process for the removal of mercaptan compounds from an 011containing the same which comprises contacting said oil in an initialstage with an alkali metal hydroxide solution, removing the treated oiland contacting the same in a secondary stage with ethylene oxide in thepresence of an aqueous solution of an alkali metal hydroxide.

ERVING ARUNDALE. JOHN P. THORN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,261,866 Agruss et a1. Nov. 4,1941 FOREIGN PATENTS Number Country Date 492,789 Great Britain Sept. 27,1938 499,978 Great Britain Feb. 1, 1939

1. PROCESS FOR THE CONVERSION OF MERCAPTAN COMPOUNDS IN A PETROLEUM OILCONTAINING THE SAME INTO RELATIVELY INNOCUOUS COMPOUNDS WHICH COMPRISESCONTACTING SAID PETROLEUM OIL WITH AN ALKYLENE OXIDE IN THE PRESENCE OFAN ALKALINE CATALYST, SAID ALKYLENE OXIDE BEING SELECTED FROM THE CLASSOF COMPOUNDS REPRESENTED BY THE STRUCTURAL FORMULA